1a.Objectives (from AD-416):
Specific objectives of this research include:
Objective 1. Provide management guidelines to improve the conservation and enhancement of agroecosystem function and structure in grasslands of the NGP.
Objective 2. Improve the viability of cattle production on the NGP by providing management strategies that increase the efficiency of forage utilization.
Objective 3. Develop methods to alter the composition of beef so that it better meets the emerging market demand for healthier beef.

1b.Approach (from AD-416):
An automated rainout shelter will be used to simulate drought conditions and test if early-season water stress and (or) defoliation following water stress will have greater impact on productivity of switchgrass or western wheatgrass or on mixtures of western wheatgrass and alfalfa. The influence of soil attributes on growth characteristics of perennial grasses will be determined with greenhouse evaluations using soil collected under native vegetation and under severely weed invaded plant communities at four sites between Mandan, ND and Pierre, SD. Field-based estimates of the greenhouse gases carbon dioxide and nitrous oxide will be used to determine if soil emissions of nitrous oxide offset carbon uptake by moderately grazed mixed-grass prairie. Satellite-based estimates of plant canopy carbon:nitrogen ratio will be determined for five native rangeland pastures and these estimates will be used to determine if they can be used to estimate forage quality for pastures on the northern Great Plains. Trials with cattle will be conducted to determine if grazing higher quality forages with supplemental flaxseed and (or) forages containing condensed tannin will result in reduced methane emissions per unit of beef produced and greater economic returns. Other trials with cattle will be conducted to determine if omega-3 fatty acid levels in beef can be raised substantially if fattening yearlings are fed flaxseed or flaxseed oil that is treated to protect the alpha-linolenic acid in it from hydrogenation by ruminal microbes.

3.Progress Report:
Research was completed for Sub-objective 1.1 (Determine the impact of drought and defoliation timing on persistence and productivity of monocultures of switchgrass or western wheatgrass and on mixtures of western wheatgrass with alfalfa) and a manuscript was prepared for publication.

For Sub-objectives 1.2 and 1.3, outreach materials were prepared for publication.

A manuscript for Sub-objective 2.3 (Develop management techniques to reduce greenhouse gas emissions by cattle) was published in Rangeland Ecology and Management. A preference trial with cattle and grape seed tannin in water was conducted, and research continues with trials with cattle to develop "tannin tea" for livestock consumption.

Research was completed for Sub-objective 3.1 (Evaluate strategies for optimizing omega-3 fatty acids in beef) and a manuscript on this research has been accepted for publication in the Journal of Animal Science. Also, an in vitro trial was conducted to evaluate protective treatments for omega-3 containing flaxseed and echium seeds that could improve their use as omega-3 containing feedstuffs for cattle and sheep.

4.Accomplishments
1.
Improving nitrogen use efficiency in cattle and sheep. Ingestion of small amounts of naturally-occurring tannins in plants by cattle and sheep has potential benefits including more efficient feed nitrogen use and reduced emissions of nitrogen. Tannin-containing plants, however, are difficult to grow. ARS scientists at the Northern Great Plains Research Laboratory in Mandan, North Dakota tested a system of providing plant tannins to cattle and sheep via their drinking water. They found that blood serum urea concentration, which is an indicator of nitrogen use, was reduced when cattle and sheep consumed water spiked with tannin indicating more efficient use of feed nitrogen. In a second trial, they found that when sheep drank water supplemented with tannin they excreted less urea in their urine also indicating more efficient use of feed nitrogen. Supplementing cattle and sheep with tannins in drinking water can reduce the amount of nitrogen excreted in urine, which improves feed nitrogen efficiency and potentially reduces nitrogen emissions to the air.

2.
Increasing omega-3 fatty acids in beef and lamb. Evidence points to human health benefits from greater consumption of omega-3 fatty acids. ARS scientists at the Northern Great Plains Research Laboratory in Mandan, North Dakota conducted two studies to determine if omega-3 fatty acids could be increased in the meat of lambs and steers by feeding them flaxseed specially treated to protect fatty acids from breakdown during digestion. Consumption of the treated flaxseed raised omega-3 fatty acid concentrations in the blood and shoulder muscle of lambs and in the blood of steers but did not raise omega-3 fatty acids in the loin muscle of steers. Supplementing the diets of forage-fed lambs with treated flaxseed can increase omega-3 fatty acids in the meat; however, more effective flaxseed treatments are needed to protect fatty acids in flaxseed fed to cattle on grain-based diets.